I took the liberty of updating a few things in the plugin including the database error because I really wanted to use it and the developer seems to have disappeared. If he ever comes back, I'll be happy to remove my link. Deactivate the current version of the plugin and delete it. Then upload this zip file to install the updated version... and you should be back online.

I've also fixed the DNS blacklist issues. The queries worked, but they would return false positives. I replaced zen.spamhaus.org with the two correct servers: sbl.spamhaus.org and xbl.spamhaus.org.

I also updated the gethostbyname logic to prevent false positives. It will only show the banned ip error if one of the proper DNS blacklist servers recognizes the IP address.

I don't have much time to maintain a plugin, but I did fix what wasn't working for me -- and what most people are complaining about on here. I cannot guarantee that I'll be able to fix any other issues as I seldom have time to visit the forums.